Disclosed in Japanese Patent Publication No. 6-63125 is an example of a full-face-type helmet, in the cap body of which a ventilator is provided, as described above, for defogging the inner surface of a shield plate and for air-ventilating within the cap body.
The full-face-type helmet described in Japanese Patent Publication No. 6-63125 (hereinafter described only as a conventional helmet) has an upper ventilator and a lower ventilator provided above and below a window opening, respectively, the window opening being provided in the full-face-type cap body so as to be opposite to the face of a person with the helmet on, when the helmet is put on the head of the person with the helmet on, such as the rider of the motorcycle or the like (hereinafter described only as the rider or the like). The upper ventilator and the lower ventilator have an upper supply air passage and a lower supply air passage, respectively, which can open and close with an upper shutter member and a lower shutter member, respectively.
In the conventional helmet, thus, the inside of the cap body (that is, the structure within the cap body and/or the inner space for the head to be fitted) can be ventilated when the outer air is led therein under the open state of the upper supply passage and, under the open state of the lower supply passage, fogging the shield plate can be prevented due to the open air led into the cap body near the lower end of the inner surface of the shield plate, and flowed up along the inner surface of the shield plate.
However, in the conventional helmet constituted as described above, the outer air led into the cap body near the lower end of the inner surface of the shield plate through the lower supply passage is not only flowed up along the inner surface of the shield plate. A considerable part of the outer air is naturally diffused wide in the cap body, so that the defogging of the shield plate becomes insufficient. Thus, in the conventional helmet, fogging the shield plate can not effectively be prevented in the humid rainy weather.